1. Field of the Invention
The present invention pertains to locks that are designed to provide an alarm when an improper key or other means such as lock picks are utilized.
In the provision of locks such as door locks for buildings and the like it is customary to have a cylinder mechanism including a cylinder body having a plug rotatable therein. The plug has a keyway into which a proper key can be introduced. The cylinder body has pin bores in it extending into the plug bore and containing first pins that are slidable in the bores and are urged toward the keyway by springs. Also there are provided pin openings in the plug communicating with the keyway and in one rotated position of the plug also communicating with the pin bores. The mechanism can readily be operated by a proper key introduced into the keyway and setting the first pins and the second pins in appropriate relationship with their abutting faces coinciding with the shear line of the plug in the cylinder body. There are instances in which the attempted operation of the lock either by an improper key or other means such as lock picks should be evidenced, by an alarm or other informational output.
2. Description of the Prior Art
Various types of alarm actuating mechanisms are disclosed in the prior art whereby unauthorized entry into a locked premises is sensed and indicated by the operation of an alarm. However, all too often mechanisms of this type have been able to be defeated so that the alarm is not actuated upon the occurrence of an unauthorized entry; and, even where the alarm is actuated, this usually occurs after the entry has taken place. As the security technology has advanced the development of means to nullify the improvements has also advanced. Thus, there has been a long standing need for a tamperproof lock mechanism which, while operable to permit authorized entry, resists unauthorized entry and may be combined with means to actuate an alarm upon attempted unauthorized entry.
The present invention contemplates a key actuated lock mechanism of the class described which is exceedingly difficult, if not impossible, to manipulate without a proper key and which may be associated with alarm actuating means so that, if even partially manipulated, it will actuate an alarm.
Locks having an alarm system associated therewith are illustrated in the prior art as set forth in U.S. Pat. Nos. 3,500,670, 3,967,481, and 3,986,376. A common aspect of each of these prior art patents is that the alarm actuating aspect is associated with the vertically disposed tumbler pins which are loaded by coil springs to prevent vertical displacement unless the proper key is inserted within the key slot. The present invention does not interrelate the movement of the tumbler pins to actuation of the alarm system associated with the invention.